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Review
. 2019 Sep 25;11(10):2288.
doi: 10.3390/nu11102288.

Dietary Quercetin and Kaempferol: Bioavailability and Potential Cardiovascular-Related Bioactivity in Humans

Wijdan M Dabeek  1 , Melissa Ventura Marra  2
Affiliations
Review

Dietary Quercetin and Kaempferol: Bioavailability and Potential Cardiovascular-Related Bioactivity in Humans

Wijdan M Dabeek et al. Nutrients. .

Abstract

Fruit and vegetable intake has been associated with a reduced risk of cardiovascular disease. Quercetin and kaempferol are among the most ubiquitous polyphenols in fruit and vegetables. Most of the quercetin and kaempferol in plants is attached to sugar moieties rather than in the free form. The types and attachments of sugars impact bioavailability, and thus bioactivity. This article aims to review the current literature on the bioavailability of quercetin and kaempferol from food sources and evaluate the potential cardiovascular effects in humans. Foods with the highest concentrations of quercetin and kaempferol in plants are not necessarily the most bioavailable sources. Glucoside conjugates which are found in onions appear to have the highest bioavailability in humans. The absorbed quercetin and kaempferol are rapidly metabolized in the liver and circulate as methyl, glucuronide, and sulfate metabolites. These metabolites can be measured in the blood and urine to assess bioactivity in human trials. The optimal effective dose of quercetin reported to have beneficial effect of lowering blood pressure and inflammation is 500 mg of the aglycone form. Few clinical studies have examined the potential cardiovascular effects of high intakes of quercetin- and kaempferol-rich plants. However, it is possible that a lower dosage from plant sources could be effective due to of its higher bioavailability compared to the aglycone form. Studies are needed to evaluate the potential cardiovascular benefits of plants rich in quercetin and kaempferol glycoside conjugates.

Keywords: cardiovascular disease; flavonols; hypertension; kaempferol; quercetin.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
General structure of quercetin and kaempferol. Two phenyl rings (A and C) and a heterocyclic ring B. If R1 = OH, Quercetin; if R1 = H, Kaempferol.
Figure 2
Figure 2
General overview of dietary flavonol bioavailability. Abbreviations: LPH, lactase-phlorizin hydrolase enzyme; SGLT 1, sodium-dependent glucose transporter; ? = mechanism is not well understood.
See this image and copyright information in PMC

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